The present invention is directed in general to an apparatus and method for decreasing the locomotive smoke emissions and engine noise when the operator advances the locomotive throttle position, and more specifically to an apparatus and method that adjusts the fuel injection pressure and/or number of injections made during a transient event or operation.
Recent amendments to the United States environmental statutes and regulations require lowering of the permitted emissions from locomotive diesel engines, including visible smoke. One such requirement is the reduction in NOx emissions, which can be effected by retarding the fuel injection timing of a locomotive diesel engine. But this timing modification negatively impacts fuel consumption and, therefore, it is desirable to increase the engine compression ratio to gain back some of the fuel composition losses.
However, increasing the compression ratio also increases the visible smoke emissions at partial engine loading. The problem of visible smoke is especially acute during transient load and speed changes, i.e., when the locomotive operator advances the throttle (i.e., moves the throttle to a higher notch position) to call for higher speed and/or greater load pulling capacity (i.e., locomotive horsepower). A locomotive typically has 8 discrete notch settings called “notches”.
Smoke emissions tend to be worse when the throttle is advanced to higher throttle positions when starting from lower positions. Excessive smoke during a transient has been addressed in the past with managing the rate that the load is applied, resulting in slower load application. Such a system and method are disclosed in U.S. Pat. No. 6,892,701. In addition, injection timing may be changed during a transient to help reduce smoke. Such as system and method is disclosed in U.S. Pat. No. 6,341,596.
Currently, fuel systems on locomotives that incorporate unit pump systems are not capable of varying the fuel pressure. In this type of system, the injection event is dependant directly upon the amount of pressure in the high-pressure line. Therefore, the unit pump system has control only over the timing of the injection, or when the injection is made relative to the top dead center position of the piston. Moreover, the injection pressure cannot be varied for a fixed speed and horsepower of the locomotive.
Other fuel systems such as the common rail fuel systems allow for more flexibility in developing fuel injection strategies. The injection event (or opening of the needle valve in the injector) is controlled by an electronic control unit (controller) and solenoid, and is not dependant on pressure in the high-pressure fuel lines leading to the injector. Such advanced fuel systems allow for fuel injection to take place at any time during the piston cycle and allow for multiple injections during a single cycle. In addition, the injection pressure is variable relative to the speed of the vehicle. A common rail fuel system for a locomotive engine is disclosed in a commonly United States published patent application, Pub. No. 20070012294.